Multichannel Systems STG4004+STG4008 Manual - Manual (Page 101)

Troubleshooting
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12.7 Signal is not Repeated / Pulse Train Fails
The STG fails to generate a train of pulses. When a pulse is programmed in MC_Stimulus and then
repeated (in the Trigger Settings dialog box) (with the Repeat option), the STG abruptly stops
after it has generated the waveform only once. (If another STG is connected to the computer to
run the same protocol, the stimulator has no problems on repeating the pulse.)
Possible causes:
? If you change the stimulus protocol after the download, even if only the number of repeats
were changed, you need to download the modified stimulus protocol to the STG. Otherwise,
the changes will not be applied. (If another STG is connected to the computer, you will have
to download the stimulus protocol, including the changes, to be able to stimulate at all.)
 Select Download or Download and Start on the STG menu (or on the toolbar) after you
made any changes to the stimulus protocol in the MC_Stimulus program.
12.8 Internal Calibration Signals
The STG emits sometimes autonomous high frequency signals.
Cause:
During the first ten minutes after starting the STG, the device emits every minute high frequency
signals (small bursts) for internal offset calibration of the current outputs in a range of +/- 10 mV.
After warming up the STG, the calibration signals later will be delivered half-hourly.
The calibration is interrupted during stimulation.
High sensitive measuring equipments will monitor these calibration signals.
Biological signals are usually slower than the high frequency bursts and will not interfere with
the calibration signals.
When monitoring the experimental signals with MC_Rack software, you do not see the calibration
signals, because MC_Rack automatically applies a 3 kHz low pass filter during data acquisition,
and a 10 kHz low pass filter during filter activities.
When using MC_Stimulus II Version 3.3 and higher it is possible to avoid the internal offset
calibration. Enable the command “Disable Autocalibration” in main menu “STG” and download
the command to the STG.